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Abstract:

The present invention provides a method for manufacturing a stator
configured to ensure insulation properties between a conductor and an
armature core while preventing a manufacturing cost from increasing and
preventing a space factor from lowering. In an edge-removing step, a
plurality of independent edge-removing punches, which correspond to one
slot S or two or more slots S press and chamfer a corner portion of an
axial opening edge of the slot in an axial end core sheet of the armature
core.

Claims:

1. A method for manufacturing a stator, the stator including: an armature
core formed by laminating a plurality of plate-like core sheets in an
axial direction of the armature core, each of the core sheets including
an annular yoke forming portion and a plurality of tooth forming portions
which inwardly extend in a radial direction of the armature core from the
yoke forming portion, the armature core including an annular portion
having the laminated yoke forming portions, a plurality of teeth
including the laminated tooth forming portions and inwardly extending in
the radial direction from the annular portion, and a plurality of slots
each formed between a circumferentially adjacent pair of the teeth; a
plurality of conductors, which constitute a coil, are inserted into the
slots and are bent in the circumferential direction at positions near
axial openings of the slots; and sheet-like insulating members, which
respectively cover inner peripheral surfaces of the slots and are located
between the armature core and the conductors, the method comprising a
pressing step for removing the edge of a corner portion of an axial
opening edge of the slot in the core sheets that is located at least at
an axial end of the armature core, wherein, the corner portion is pressed
and chamfered by a plurality of independent edge-removing punches, each
of which correspond to one slot or two or more slots.

2. The method for manufacturing a stator according to claim 1, wherein
each of the edge-removing punches includes an inserting portion, the
inserting portion includes an outer peripheral surface corresponding to
an inner peripheral surface of the slot, and the inserting portion is
inserted into the slot from its distal end.

3. The method for manufacturing a stator according to claim 1, wherein
the number of the edge-removing punches is equal to the number of the
slots, and the edge-removing punches independently correspond to the
slots, respectively.

4. The method for manufacturing a stator according to claim 1, wherein in
the pressing step, the corner portion is pressed by the edge-removing
punch in a state where the armature core is restrained from radial inner
side and outer side of the armature core.

5. The method for manufacturing a stator according to claim 1, wherein in
the pressing step, the corner portion is pressed by the edge-removing
punch in a state where distal ends of the teeth and the annular portion
are restrained from the axial direction.

6. The method for manufacturing a stator according to claim 5, wherein
each of the yoke forming portions includes a fixing portion for fixing,
to each other, the yoke forming portions that are adjacent to each other
in the axial direction, and in the pressing step, a region of the annular
portion that includes the fixing portion is restrained from the axial
direction.

7. The method for manufacturing a stator according to claim 1, wherein
each of the teeth includes a rotor facing portion projecting in the
circumferential direction in a distal end of the tooth, a slit, which
opens inside of the slot and radially inward of the armature core, is
formed between distal end surfaces of each circumferentially adjacent
pair of the rotor facing portions, and in the pressing step, the corner
portion is pressed by the edge-removing punch in a state where distal end
restraining portions, which restrain distal ends of the teeth from the
circumferential direction, are inserted into each of the slits.

8. The method for manufacturing a stator according to claim 7, wherein in
the pressing step, the corner portion is pressed by the edge-removing
punch in a state where the annular portion and the distal ends of the
teeth are restrained from the axial direction, and the magnitude of a
restraining force per unit area to restrain the annular portion from the
axial direction is greater than the magnitude of a restraining force per
unit area to restrain the distal ends of the teeth from the axial
direction.

9. The method for manufacturing a stator according to claim 1, wherein in
the pressing step, the corner portion is pressed by the edge-removing
punch and the armature core is separated from the edge-removing punch in
a state where radial central portions of the teeth are restrained from
the axial direction.

10. The method for manufacturing a stator according to claim 1, further
comprising a conductor inserting step for inserting the conductor into
the insulating member from the axial direction, wherein the conductor
includes two straight portions and a connecting portion, which connects
the straight portions to each other, and the conductor is a substantially
U-shaped segment conductor.

11. The method for manufacturing a stator according to claim 1, wherein a
first core sheet group including at least one or some of the core sheets
whose corner portion is chamfered is made of magnetic material that is
softer than silicon steel sheet, and the core sheets other than the first
core sheet group are made of silicon steel sheet.

12. A stator comprising: an armature core formed by laminating a
plurality of plate-like core sheets in an axial direction of the armature
core, each of the core sheets including an annular yoke forming portion
and a plurality of tooth forming portions which inwardly extend in a
radial direction of the armature core from the yoke forming portion, the
armature core including an annular portion having the laminated yoke
forming portions, a plurality of teeth including the laminated tooth
forming portions and inwardly extending in the radial direction from the
annular portion, and a plurality of slots each formed between a
circumferentially adjacent pair of the teeth; a plurality of conductors,
which constitute a coil, are inserted into the slots and are bent in the
circumferential direction at positions near axial openings of the slots;
and insulating members, which respectively cover inner peripheral
surfaces of the slots and are located between the armature core and the
conductors, wherein a corner portion of an axial opening edge of the slot
is chamfered in the core sheet that is located at least at one axial end
of the armature core.

13. The stator according to claim 12, wherein each of the yoke forming
portions includes a fixing portion for fixing, to each other, the yoke
forming portions that are adjacent to each other in the axial direction,
and the fixing portion is located on an extension line of a center line
of the tooth forming portion that passes through a center of the tooth
forming portion in its circumferential direction, and the fixing portion
extends in the radial direction.

14. The stator according to claim 12, wherein the conductor includes two
straight portions and a connecting portion, which connects the straight
portions to each other, and the conductor, is a substantially U-shaped
segment conductor.

15. The stator according to claim 12, wherein a first core sheet group
including at least one or some of the core sheets whose corner portion is
chamfered is made of magnetic material that is softer than silicon steel
sheet, and the core sheets other than the first core sheet group are made
of silicon steel sheet.

16. A motor comprising: the stator according to claim 12; a
consequent-pole type rotor, which includes an annular rotor core and a
plurality of magnets fixed to the rotor core and is located inside of the
stator, wherein the conductor includes two straight portions and a
connecting portion, which connects the straight portions to each other,
and the conductor is a substantially U-shaped segment conductor, and the
rotor includes a small magnetic lightweight portion having specific
gravity and magnetic properties smaller than specific gravity and
magnetic properties of a rotor core material constituting the rotor core.

Description:

TECHNICAL FIELD

[0001] The present invention relates to a method for manufacturing a
stator, a stator manufactured by the manufacturing method, and a motor
having the stator.

BACKGROUND ART

[0002] A stator described in Japanese Laid-Open Patent Publication No.
2009-38918 includes an armature core formed by laminating a plurality of
core sheets on one another. A plurality of teeth extending in a radial
direction of the armature core, and a plurality of slots are formed in
the armature core. Sheet-like insulating members are inserted into the
slots, and conductors are inserted into the insulating members. The
insulating members located between the armature core and the conductors
ensure insulation properties between the armature core and the
conductors. It is known that if the stator is provided with SC coils,
i.e., segment conductor coils, the space factor of the coils is
increased.

[0003] In the stator described in Patent Document 1, ends of each tooth in
an axial direction thereof are provided with soft portions. According to
this configuration, when the conductor inserted into the slot is bent in
the circumferential direction, it is possible to prevent the insulating
member located between the armature core and the conductor from being
damaged by a corner portion of an axial opening of the slot.

[0004] However, if the ends of the teeth in the axial direction are
provided with such soft portions, additional soft portions must be
provided separately from existing parts that configure the stator, such
as the armature core, the conductors, and the insulating members. This
increases the manufacturing costs. Further, to more effectively prevent
the insulating member from being damaged by the soft portions, it is
desirable that the soft portions be made to project inward of the slots
to prevent the insulating members from coming into contact with the
corner portions. In this case, however, the space factor of the coils is
lowered.

[0005] The present invention has been accomplished in view of such
circumstances, and it is an objective of the invention to provide a
method for manufacturing a stator, a stator and a motor configured to
ensure insulation properties with respect to conductors, and an armature
core, while preventing the manufacturing costs from increasing and
preventing the space factor from lowering.

Means for Solving the Problems

[0006] To achieve the foregoing objective and in accordance with one
aspect of the present invention, a method for manufacturing a stator is
provided. The stator includes an armature core, a plurality of
conductors, and sheet-like insulating members. The armature core is
formed by laminating a plurality of plate-like core sheets in an axial
direction of the armature core. Each of the core sheets includes an
annular yoke forming portion and a plurality of tooth forming portions
which inwardly extend in a radial direction of the armature core from the
yoke forming portion. The armature core includes an annular portion
having the laminated yoke forming portions, a plurality of teeth
including the laminated tooth forming portions and inwardly extending in
the radial direction from the annular portion, and a plurality of slots
each formed between a circumferentially adjacent pair of the teeth. The
conductor constitute a coil, are inserted into the slots and are bent in
the circumferential direction at positions near axial openings of the
slots. The sheet-like insulating members respectively cover inner
peripheral surfaces of the slots and are located between the armature
core and the conductors. The method includes a pressing step for removing
the edge of a corner portion of an axial opening edge of the slot in the
core sheets that is located at least at an axial end of the armature
core. The corner portion is pressed and chamfered by a plurality of
independent edge-removing punches, each of which correspond to one slot
or two or more slots.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007]FIG. 1 is a cross-sectional view of a motor according to one
embodiment of the present invention;

[0008]FIG. 2 is an exploded perspective view of an armature core in the
embodiment;

[0009]FIG. 3 is a partial cross-sectional view of a stator and a rotor in
the embodiment;

[0018] FIG. 10(a) is a schematic diagram of a pressing device in a state
where it restrains the armature core;

[0019] FIG. 10(b) is a schematic diagram of the pressing device when the
armature core is subjected to press working;

[0020]FIG. 11 is a cross-sectional view of an armature core restrained by
a radially inner restraining metal core;

[0021]FIG. 12 is an enlarged partial perspective view of an edge-removing
punch;

[0022]FIG. 13(a) is an enlarged partial view of the pressing device in a
state where it restrains the armature core;

[0023]FIG. 13(b) is an enlarged partial view of the pressing device when
the armature core is subjected to press working;

[0024]FIG. 14 is an explanatory diagram for explaining a region where the
armature core is restrained from the axial direction in a pressing step;

[0025]FIG. 15 is a diagram for explaining an insulating member inserting
step;

[0026] FIG. 16 is a diagram for explaining a conductor inserting step; and

[0027] FIG. 17 is an enlarged partial cross-sectional view of the stator
for explaining a bending step.

MODES FOR CARRYING OUT THE INVENTION

[0028] One embodiment of the present invention will now be described with
reference to the drawings.

[0029] As shown in FIG. 1, a motor 1 includes a motor case 2. The motor
case 2 includes a cylindrical housing 3, which is formed into a
cylindrical shape with a closed end, and a front end plate 4, which
closes an opening formed in a front side (left side in FIG. 1) of the
cylindrical housing 3. A circuit accommodating box 5 is mounted on a rear
end (right side in FIG. 1) of the cylindrical housing 3, and a power
supply circuit such as a circuit substrate is accommodated in the circuit
accommodating box 5.

[0030] A stator 6 is fixed to the inner peripheral surface of the
cylindrical housing 3. The stator 6 includes an armature core 7. The
armature core 7 is formed by laminating a plurality of core sheets 11
made of steel on one another in an axial direction of the armature core
7.

[0031] As shown in FIG. 2, two core sheets 11 located on both axial ends
of the core sheets 11, i.e., an upper end core sheet 11a and a lower end
core sheet 11b are made of magnetic material that is softer than silicon
steel sheet, such as SPCC (cold rolled steel sheet). The other core
sheets 11 excluding the core sheets 11a and 11b are made of silicon steel
sheet. The core sheets 11 are formed by punching these metal sheet
materials by press work.

[0032] As shown in FIGS. 2 and 3, the shape of each core sheet 11 as
viewed in the axial direction is the same as the shape of the armature
core 7 as viewed in the axial direction. Each of the core sheets 11
includes an annular plate-like yoke forming portion 12 and a plurality of
(sixty in the present embodiment) comb-shaped plate-like tooth forming
portions 13 extending inward in a radial direction of the armature core 7
from the yoke forming portion 12. The tooth forming portions 13 are
formed at equal angular intervals (6° intervals in the present
embodiment) in the circumferential direction of the armature core 7. Slot
forming portions 14 are each formed between a circumferentially adjacent
pair of the tooth forming portions 13.

[0033] As shown in FIGS. 2 to 4, a plurality of (twelve in the present
embodiment) fitting projections 15 are formed on one side of the yoke
forming portion 12 of each of the core sheets 11 in the thickness
direction (axial direction) of the yoke forming portion 12, and fitting
recesses 16, the number of which corresponds to the number of the fitting
projections 15, are formed in the other side (lower side in FIG. 4) in
the thickness direction of the yoke forming portion 12. In the present
embodiment, the fitting projections 15 are formed on radial outer sides
of the twelve tooth forming portions 13 arranged at 30° intervals
in the circumferential direction to correspond to the tooth forming
portions 13. Each of the fitting projections 15 is formed into a columnar
shape projecting in the axial direction and is formed on an extension
line L2 of a center line L1 of each of the tooth forming portions 13. The
center line L1 is a line passing through a center of the tooth forming
portion 13 in its width direction and extending in the radial direction.
Centers of the 12 fitting projections 15 are located on the extension
lines L2 of the center lines L1 of the 12 tooth forming portions 13,
respectively. Each of the fitting projections 15 is located at a central
portion of the yoke forming portion 12 in the radial direction.

[0034] As shown in FIG. 4, the fitting recesses 16 are formed in the yoke
forming portion 12 of the core sheet 11 on the side opposite from the
fitting projections 15 such that the fitting recesses 16 correspond to
the fitting projections 15, respectively. Each of the fitting recesses 16
is recessed in the axial direction of the yoke forming portion 12, and
the fitting recess 16 has a circle shape as viewed in the thickness
direction of the yoke forming portion 12. The inner diameter of the
fitting recess 16 is substantially equal to that of the fitting
projection 15.

[0035] As shown in FIGS. 2 and 4, the core sheets 11 are laminated such
that the yoke forming portions 12 are laminated in the thickness
direction and the sixty tooth forming portions 13 are laminated in the
thickness direction. Thus, the armature core 7 is constituted. The
fitting projections 15 of one of a pair of axially adjacent core sheets
11 are fitted into the fitting recesses 16 of the other core sheet 11.
According to this configuration, the laminated core sheets 11 are
integrally fixed to one another in the axial direction.

[0036] As shown in FIGS. 2 and 3, the yoke forming portions 12 laminated
in the axial direction form an annular portion 22. A plurality of (sixty
in the present embodiment) teeth 23 extending inward in the radial
direction of the annular portion 22 are formed by the tooth forming
portions 13 laminated in the axial direction. Sixty slots S are formed
such that each of them is located between a circumferentially adjacent
pair of the teeth 23. The slots S are formed by connecting the slot
forming portions 14 in the axial direction.

[0037] As shown in FIG. 6, a pair of rotor facing portions 23a projecting
toward both sides in the circumferential direction is formed on the
distal end of each of the teeth 23, i.e., on the radial inner end of each
of the teeth 23. The distal end surface of each of the rotor facing
portions 23a, i.e., the circumferential end surface of the rotor facing
portion 23a is formed into a flat surface 23b. The flat surface 23b
extends substantially in the radial direction and is parallel to the
axial direction. The flat surfaces 23b in each circumferentially opposed
pair are parallel to each other. The radial outer end surface of each of
the rotor facing portions 23a is formed into an inclined surface 23c,
which is inclined to separate away from the annular portion 22 from the
proximal end to the distal end of the rotor facing portion 23a.

[0038] Each of the slots S extends through the armature core 7 in the
axial direction. Radially inward of the slots S, slits 24 are formed such
that each is located between a circumferentially opposed pair of the flat
surfaces 23b. The circumferential width W2 of each slit 24 is narrower
than the circumferential width W1 of each slot S. Each of the slits 24
opens at both ends in the radial direction. Each slit 24 opens in the
slot on the outer side in the radial direction, and the slit 24 opens in
an inner space of the armature core 7 on the inner side in the radial
direction, i.e., opens in a space radially inward of an inner end surface
of the tooth 23. The slit 24 also opens at both sides in the axial
direction. Each of the slots S communicates with the inner space of the
armature core 7 through the slit 24. In the present embodiment, each of
the slots S is located in the space between adjacent teeth 23 and is
located radially outward of the flat surface 23b. More specifically, each
slot S is formed between a portion of a tooth 23 located radially outward
of the rotor facing portion 23a, the inclined surface 23c, and the
adjacent tooth 23 and is surrounded by the inner side surface of the
annular portion 22, which is exposed radially inward.

[0039] As shown in FIGS. 5(a) and 5(b), edge-removed portions 25 are
formed on the core sheet 11a located at one axial end of the armature
core 7. The edge-removed portions 25 are formed by pressing corner
portions K of axial opening edges of the slots S in the core sheet 11a by
press working. In the present embodiment, the edge-removed portions 25
are arcuate. Similar edge-removed portions 25 (not shown) are formed also
on the core sheet 11b located at the other end of the armature core 7 in
the axial direction.

[0040] As shown in FIG. 6, a sheet-like insulating member 26 made of
insulative plastic is inserted into each of the slots S. The thickness of
the insulating member 26 of the present embodiment is smaller than half
the circumferential width W2 of the slit 24. The insulating members 26
are inserted into the slots S from the axial direction in a state where
both ends of each insulating member 26 are folded back such that the both
ends are opposed to each other. Each insulating member 26 is shaped along
the inner peripheral surface of the corresponding slot S to cover the
inner peripheral surface of the slot S. The inner peripheral surface of
each slot S refers to portions of both circumferential side surfaces of
the teeth 23 that are located radially outward of the rotor facing
portion 23a, the inclined surface 23c, and the inner side surface of the
annular portion 22 that is exposed from between the adjacent teeth 23.
More specifically, each insulating member 26 includes two opposed
portions 26a and 26b and an edge connecting portion 26c. The opposed
portions 26a and 26b respectively cover both side surfaces of the
corresponding slot S in the circumferential direction. The edge
connecting portion 26c connects radial outer ends of the two opposed
portions 26a and 26b to each other and cover the radial outer surfaces of
the slot S. The radially inner ends of the two opposed portions 26a and
26b are located in the slit 24. The two opposed portions 26a and 26b of
each of the insulating members 26 are separated from each other in the
circumferential direction. The radially inner ends of the two opposed
portions 26a and 26b of each of the insulating members 26 cover the flat
surface 23b in the slit 24. As shown in FIGS. 7(a) and 7(b), the
insulating member 26 is formed longer than the axial length of the slot
S, and the insulating member 26 projects outward of the slot S from both
axial end openings of the slot S.

[0041] As shown in FIG. 3, three-phase (U phase, V phase and W phase)
Y-connection segment coils 28 are wound and provided in the armature core
7, and the segment coils 28 are formed by electrically connecting a
plurality of segment conductors 27 to each other. The segment conductors
27 are formed from wires having the same cross-sectional shapes. As shown
in FIGS. 7(a) and 8, each of the segment conductors 27 includes two
straight portions 27a and 27b and a connecting portion 27c, which
connects the straight portions 27a and 27b to each other. Each segment
conductor 27 is formed into a substantially U-shape. The two straight
portions 27a and 27b penetrate the slots S having different
circumferential positions and are located at different radial positions
in the slots S.

[0042] As shown in FIGS. 6 and 8, in the stator 6 of the present
embodiment, total four straight portions 27a and 27b are arranged side by
side in each slot S. Two kinds of segment conductors 27 are used. In one
of the two kinds of segment conductors 27, the two straight portions 27a
and 27b are located at first and fourth positions from the radial inner
side (a segment conductor 27x illustrated on outer side in FIG. 8), and
in the other kind of the segment conductors 27, the two straight portions
27a and 27b are located at second and third positions from the radial
inner side (a segment conductor 27y illustrated on inner side in FIG. 8).
The segment coil 28 is mainly formed from the two kinds of substantially
U-shaped segment conductors 27. A special kind of segment conductor
(e.g., segment conductor having only one straight portion) is used as a
coil end such as a power supply connecting terminal and a neutral point
connecting terminal.

[0043] As shown in FIGS. 7(a) and 8, the straight portions 27a and 27b are
inserted into the insulating members 26 and penetrate the slots S,
respectively. The distal ends of the straight portions 27a and 27b
project outside from the slots S and are bent, and the distal ends are
electrically connected to other distal ends or the special kind of
segment conductors by welding or the like. According to this
configuration, the segment coils 28 are formed by the segment conductors
27. The distal end portions of the straight portions 27a and 27b are
pressed against the edge-removed portions 25 through the insulating
members 26 and bent in the vicinity of the edge-removed portions 25. In
FIG. 8, the bent distal end portions of the straight portions 27a and 27b
are shown by phantom lines. Each of the segment conductors 27 is
electrically insulated from the armature core 7 by the insulating member
26 located between each of the segment conductors 27 and the armature
core 7.

[0044] As shown in FIG. 1, a rotor 31, which is opposed to the stator 6 in
the radial direction, is located inside of the stator 6. A rotation shaft
32 is inserted into the rotor 31 to be fixed. In the present embodiment,
the rotation shaft 32 is made of metal (preferably non-magnetic material)
and is supported by a bearing 34 fixed to a bottom 3a of the cylindrical
housing 3 and by a bearing 35 fixed to the front end plate 4.

[0045] The rotor 31 is a consequent-pole type rotor and includes an
annular rotor core 37. The rotor core 37 is formed by laminating, on one
another, a plurality of rotor core sheets 36 made of steel sheet, and the
rotor core 37 is fitted over the rotation shaft 32.

[0046] As shown in FIGS. 3 and 9, the rotor core 37 includes a cylindrical
shaft fixing tubular portion 41, a magnet fixing tubular portion 42, and
bridging portions 43. The shaft fixing tubular portion 41 is fitted over
the rotation shaft 32, and the magnet fixing tubular portion 42 surrounds
an outer side surface of the shaft fixing tubular portion 41 at a
constant distance therefrom. The bridging portions 43 connect the shaft
fixing tubular portion 41 and the magnet fixing tubular portion 42 to
each other at a constant distance therefrom.

[0047] Five sectoral recesses 42a are provided in the outer peripheral
surface of the magnet fixing tubular portion 42. These recesses 42a are
arranged at equal distances from one another in the circumferential
direction and extend through the entire outer peripheral surface of the
magnet fixing tubular portion 42 in the axial direction. Five salient
poles 44 are formed on the outer peripheral surface of the magnet fixing
tubular portion 42 between the recesses 42a.

[0048] Magnets 45 are fixed to the recesses 42a, respectively. Each of the
five magnets 45 is arranged such that the radial inner surface of each
magnet 45 is a north pole and the radial outer surface of the magnet 45,
i.e., a surface thereof on the side of the stator 6 is a south pole. As a
result, a magnetic pole of an outer side surface of a salient pole 44,
i.e., a surface of the salient pole 44 on the side of the stator 6 is a
north pole unlike the outer side surface of the magnet 45.

[0049] The number Z of the teeth 23 in the stator 6 of the present
embodiment is set in the following manner.

[0050] If the number of magnets 45 of the rotor 31 (number of pairs of
magnetic poles) is defined as p (p is integer not less than 2) and the
number of phases of the segment coils 28 is defined as m, the number Z of
teeth 23 is obtained by the following expression:

Z=2×p×m×n(where, n is a natural number).

[0051] In the present embodiment, the number Z of the teeth 23
(Z=2×5 (number of magnets 45)×3 (number of phases)×2)
is sixty.

[0052] Five bridging portions 43, which connect the shaft fixing tubular
portion 41 and the magnet fixing tubular portion 42 to each other and
hold them, are provided on the rotor 31. Each of the bridging portions 43
extends from the outer peripheral surface of the shaft fixing tubular
portion 41 and is connected to the inner peripheral surface of the magnet
fixing tubular portion 42. The bridging portions 43 are connected to the
inner peripheral surface of the magnet fixing tubular portion 42 at
positions corresponding to the recesses 42a to which the magnets 45 are
fixed. Each of the bridging portions 43 is provided such that a center
position (angle) of its circumferential direction and a center position
(angle) of the magnet 45 in the circumferential direction are located
side by side in the radial direction (angles match with each other). A
space formed between an outer side surface of the shaft fixing tubular
portion 41 and an inner side surface of the magnet fixing tubular portion
42 are divided by the bridging portions 43 into five gaps 46 which
axially extend between the shaft fixing tubular portion 41 and the magnet
fixing tubular portion 42. By forming these gaps 46, the rotor core 37
becomes light in weight, and the motor 1 can be reduced in weight.

[0053] As shown in FIGS. 1 and 3, if a drive current is supplied from a
power supply circuit in the circuit accommodating box 5 to the segment
coils 28, a rotating magnetic field for rotating the rotor 31 by the
stator 6 is generated, a magnetic flux is delivered between the teeth 23
and the rotor 31, and the rotor 31 is rotated.

[0054] Next, a method for manufacturing the stator 6 of the present
embodiment will be described.

[0055] First, a laminating step for laminating the core sheets 11 on one
another in the thickness direction to form the armature core 7 is carried
out. As shown in FIG. 2, in the laminating step, the core sheets 11 are
laminated on one another such that the yoke forming portions 12 of the
core sheets 11 are laminated on one another in the thickness direction
(axial direction) and the sixty tooth forming portions 13 are laminated
on one another in the thickness direction. At that time, as shown in FIG.
4, 12 fitting recesses 16 of one of the two adjacent core sheets 11 and
twelve fitting projections 15 of the other core sheet 11 are superposed
on each other in the thickness direction (axial direction) of the core
sheets 11. The laminated core sheets 11 are integrally fixed to one
another in the axial direction. At that time, the fitting projections 15
of one of the two adjacent core sheets 11 are press-fitted into the
fitting recesses 16 of the other core sheet 11. According to this
press-fitting, the adjacent core sheets 11 are fixed to each other
(integrally formed together). The armature core 7, including the annular
portion 22, which is formed from the axially laminated yoke forming
portions 12, and sixty teeth 23, which are formed from the axially
laminated tooth forming portions 13, is formed from the core sheets 11.
In the armature core 7, the two core sheets 11 located on both the axial
ends, i.e., the core sheets 11a and 11b are made of magnetic material
(e.g., SPCC (cold rolled steel sheet)) that is softer than silicon steel
sheet, and the other core sheets 11 are made of silicon steel sheet.

[0056] Next, an edge-removing step for removing the edges the corner
portions K of the axial opening edges of the slots S in each of the core
sheets 11a and 11b is carried out. In the edge-removing step, the corner
portions K are arcuately chamfered by subjecting the corner portions K to
press working.

[0057] A pressing device 51 used in the edge-removing step will be
described with reference to FIGS. 10 to 14. As shown in FIGS. 10(a) and
10(b), the pressing device 51 includes a lower die 61 and an upper die 71
located above the lower die 61.

[0058] First, the lower die 61 will be described. A plate-like die plate
63 is placed on the upper surface of a plate-like lower die stage 62. A
plurality of first insertion holes 63a are formed in the die plate 63 to
vertically extend through the die plate 63, and first knockout pressing
pins 64 are respectively inserted into the first insertion holes 63a such
that the first knockout pressing pins 64 can move in the vertical
direction relative to the die plate 63. In the lower die stage 62, first
accommodation holes 62a are formed at positions that are adjacent to the
first insertion holes 63a in the vertical direction, and the proximal
ends (lower ends) of the first knockout pressing pins 64 are accommodated
in the first accommodation holes 62a. The first springs 65, which
upwardly urge the proximal ends of the first knockout pressing pins 64,
are respectively accommodated in the first accommodation holes 62a.

[0059] An annular radially outer restraining ring 66 is placed on the
upper surface of the die plate 63. The radially outer restraining ring 66
is located on the die plate 63 such that the radially outer restraining
ring 66 cannot move relative to the die plate 63. The vertical length of
the radially outer restraining ring 66 is longer than the axial length of
the armature core 7. A restraining hole 66a having a circular cross
section is formed at a radial central portion of the radially outer
restraining ring 66, and the restraining hole 66a extends through the
radially outer restraining ring 66 in the vertical direction. The inner
diameter of the restraining hole 66a is substantially equal to the outer
diameter of the armature core 7 and in the present embodiment, the inner
diameter of the restraining hole 66a is slightly greater than the outer
diameter of the armature core 7. The axial length, i.e., the vertical
length of the restraining hole 66a is longer than the axial length of the
armature core 7. A first stopper recess 66b is formed at the lower end of
the radially outer restraining ring 66, and the first stopper recess 66b
is upwardly recessed at the outer peripheral edge of the lower opening of
the restraining hole 66a.

[0060] An annular lower knockout plate 67 is located inside of the
radially outer restraining ring 66. A flange-like first stopper 67a
extending radially outward is formed at the lower end of the lower
knockout plate 67. The outer diameter of the first stopper 67a is
substantially equal to the inner diameter of the first stopper recess
66b, and an axial thickness (vertical thickness) of the first stopper 67a
is smaller than a depth (vertical depth) of the first stopper recess 66b.
The first stopper 67a is located in the first stopper recess 66b, and the
first stopper 67a can vertically move between the upper surface of the
die plate 63 and the bottom surface of the first stopper recess 66b.

[0061] The outer diameter of the lower knockout plate 67 except for the
first stopper 67a, i.e., the outer diameter of a portion of the lower
knockout plate 67 located higher than the first stopper 67a is
substantially equal to the inner diameter of the restraining hole 66a.
The upper end of the lower knockout plate 67 is inserted into the
restraining hole 66a. The axial length of a portion of the lower knockout
plate 67 located higher than the first stopper 67a is shorter than the
axial length of the restraining hole 66a. A through hole 67b is formed in
a radial central portion of the lower knockout plate 67, and the through
hole 67b extends through the lower knockout plate 67 in the axial
direction. The inner diameter of the through hole 67b is substantially
equal to the inner diameter of the armature core 7. The upper surface of
the lower knockout plate 67 is a flat lower pressing surface 67c, and the
lower pressing surface 67c intersects (horizontal) with an axial
direction of the lower knockout plate 67 at right angles. The distal end
surface of the first knockout pressing pin 64 abuts against the lower end
surface of the lower knockout plate 67.

[0062] A columnar radially inner restraining metal core 68 located inside
of the lower knockout plate 67. The radially inner restraining metal core
68 is arranged coaxially with the radially outer restraining ring 66 and
the lower knockout plate 67. The lower end of the radially inner
restraining metal core 68 is fixed to the die plate 63. The axial length
of the radially inner restraining metal core 68 is longer than the axial
length of the radially outer restraining ring 66, and both axial ends of
the radially inner restraining metal core 68 project toward both axial
sides of the radially outer restraining ring 66.

[0063] As shown in FIG. 11, the radially inner restraining metal core 68
includes a vertically extending columnar radially inner restraining
portion 68a, and a plurality of (sixty in the present embodiment) distal
end restraining portions 68b formed on the outer peripheral surface of
the radially inner restraining portion 68a. The outer diameter of the
radially inner restraining portion 68a is substantially equal to the
inner diameter of the armature core 7 and is slightly smaller than the
inner diameter of the armature core 7 in the present embodiment.

[0064] Each of the distal end restraining portions 68b projects radially
outward from the outer peripheral surface of the radially inner
restraining portion 68a and is formed into an elongated projection
extending in the axial direction. The distal end restraining portions 68b
are formed on the outer peripheral surface of the radially inner
restraining portion 68a at equal angles (6° in the present
embodiment) in the circumferential direction to correspond to the slits
24 formed in the armature core 7. The circumferential width of the distal
end restraining portion 68b is substantially equal to (slightly narrower
than) the circumferential width of the slit 24, and the circumferential
length of the distal end restraining portion 68b is slightly shorter than
the radial length of the slit 24.

[0065] Next, the upper die 71 will be described. As shown in FIGS. 10(a)
and 10(b), the plate-like punch plate 73 is located under a plate-like
upper die stage 72 such that the punch plate 73 abuts against the lower
surface of the upper die stage 72. A plurality of second insertion holes
73a are formed in the punch plate 73 such that the second insertion holes
73a extend through the punch plate 73 in the vertical direction. Second
knockout pressing pins 74 are respectively inserted into the second
insertion holes 73a such that the second knockout pressing pins 74 can
vertically move relative to the punch plate 73. A plurality of second
accommodation holes 72a are formed in positions where the second
accommodation holes 72a are adjacent to the second insertion holes 73a in
the vertical direction on the upper die stage 72. The proximal ends
(upper ends) of the second knockout pressing pins 74 are accommodated in
the second accommodation holes 72a. Second springs 75, which downwardly
urge the proximal ends of the second knockout pressing pins 74, are
respectively accommodated in the second accommodation holes 72a.

[0066] The punch plate 73 holds a plurality of edge-removing punches 76 on
an inner side of the second insertion holes 73a, and the number of the
edge-removing punches 76 is the same as that of the slots S formed in the
armature core 7 and is sixty. The edge-removing punches 76 are provided
independently to correspond to the slots S, respectively. Each
edge-removing punch 76 includes a plate-like base portion 76a, and a
pressing portion 76b axially extending from the base portion 76a. The
base portion 76a of the edge-removing punch 76 is accommodated in a
holding recess 73b formed in the upper end of the punch plate 73 and held
between the bottom surface of the holding recess 73b and the lower
surface of the upper die stage 72. The pressing portions 76b of the
edge-removing punches 76 are inserted into insertion holes 73c, which
extend through the bottom of the holding recess 73b. The sixty
edge-removing punches 76 held by the punch plate 73 are independently
located at the same distances (at 6° intervals in circumferential
direction in the present embodiment), from one another, as those of the
slots S.

[0067] The pressing portions 76b substantially have a square pole shape
axially extending from the lower end surface of the base portions 76a. As
shown in FIGS. 10(a) and 12, each pressing portion 76b is provided at its
distal end with an inserting portion 76c. The inserting portions 76c are
also of a square pole shape that is thinner than a portion of the
pressing portion 76b on the side of its proximal end. The cross-sectional
shape of a portion of each pressing portion 76b located closer to the
proximal end than the inserting portion 76c is a rectangle greater than
the cross-sectional shape of each slot S. The outer shape of each
inserting portion 76c is substantially the same as the inner peripheral
surface shape of each slot S, and the cross-sectional shape that
intersects the axial direction of the inserting portion 76c at right
angles is substantially the same as the cross-sectional shape of the slot
S. That is, the inserting portion 76c has an outer peripheral surface
corresponding to the inner peripheral surface of the slot S. A truncated
square pyramid-shaped introducing portion 76d is formed on the distal end
of each inserting portion 76c. The introducing portion 76d becomes
thinner toward the distal end of the inserting portion 76c. The pressing
portions 76b of the sixty edge-removing punches 76 can be inserted into
the sixty slots of the armature core 7 from the axial direction.

[0068] As shown in FIGS. 12 and 13A, an edge-removing surface 76e is
formed on the proximal end of each inserting portion 76c. More
specifically, the edge-removing surface 76e is formed in a region of the
outer peripheral surface of the proximal end of each inserting portion
76c that corresponds to the axial opening peripheral edge of the
corresponding slot S when the pressing portion 76b is inserted into the
slot S. The edge-removing surfaces 76e are arcuately curved for removing
the edges of the corner portions K in the slots S. In the present
embodiment, a curvature radius R of the edge-removing surface 76e is set
greater than the thickness of the core sheet 11. As shown in FIG. 13(b),
the edge-removing surface 76e is formed such that when it is pressed by
the corner portions K of the core sheets 11a and 11b located on both
axial ends of the armature core 7, the edge-removing surface 76e does not
come into contact with core sheets 11 that are adjacent to the core
sheets 11a and 11b, i.e., second core sheets 11 from the both axial ends
of the armature core 7.

[0069] As shown in FIG. 10(a), an annular knockout holder 77 is located
below the punch plate 73. The knockout holder 77 abuts against the lower
surface of the punch plate 73. The knockout holder 77 cannot move
relative to the punch plate 73 and is arranged coaxially with the
edge-removing punches 76. A guide hole 77a having a circular cross
section is formed in a radial central portion of the knockout holder 77,
and the guide hole 77a extends through the knockout holder 77 in the
vertical direction. The inner diameter of the guide hole 77a is
substantially equal to the outer diameter of the armature core 7 and in
the present embodiment, the inner diameter is slightly greater than the
outer diameter of the armature core 7. A second stopper recess 77b is
formed in the upper end of the radially outer restraining ring 66. The
second stopper recess 77b is recessed downward in an outer peripheral
edge of the upper end opening of the guide hole 77a.

[0070] An annular upper knockout plate 78 is arranged inside of the
knockout holder 77. The upper knockout plate 78 is arranged coaxially
with the edge-removing punches 76. A radially outwardly extending
flange-like second stopper 78a is formed at the upper end of the upper
knockout plate 78. The outer diameter of the second stopper 78a is
substantially equal to the inner diameter of the second stopper recess
77b. An axial thickness (vertical thickness) of the second stopper 78a is
smaller than a depth (vertical depth) of the second stopper recess 77b.
The second stopper 78a is located in the second stopper recess 77b and
can vertically move between the lower surface of the punch plate 73 and
the bottom surface of the second stopper recess 77b.

[0071] The outer diameter of the upper knockout plate 78 except for the
second stopper 78a, i.e., the outer diameter of a portion of the upper
knockout plate 78 located lower than the second stopper 78a is
substantially equal to the inner diameter of the guide hole 77a. A
portion of the upper knockout plate 78 located lower than the second
stopper 78a is inserted into the guide hole 77a, and this portion
penetrates the guide hole 77a and projects downward further than the
knockout holder 77.

[0072] Sixty punch insertion holes 78b into which the sixty pressing
portions 76b of the edge-removing punches 76 are respectively inserted
are formed in the upper knockout plate 78. The inner peripheral surface
of each punch insertion hole 78b has a substantially square pole shape
that corresponds to the outer shape of a portion of the corresponding
pressing portion 76b closer to the proximal end than the inserting
portion 76c. As shown in FIG. 13(a), slight gaps 79 are formed between
the inner peripheral surface of each punch insertion hole 78b and the
outer peripheral surface of the corresponding pressing portion 76b.
Similarly, as shown in FIGS. 10(a) and 10(b), slight gaps are also formed
between the outer peripheral surface of each base portion 76a and the
inner peripheral surface of the corresponding holding recess 73b and
between the outer peripheral surface of each pressing portion 76b and the
inner peripheral surface of the corresponding insertion hole 73c.
According to this configuration, the edge-removing punches 76
independently float with respect to the punch plate 73 and the upper
knockout plate 78, and the edge-removing punches 76 can follow the
position of the slot S.

[0073] As shown in FIG. 10(a), an upper pressing surface 78c is formed on
the lower end surface of the upper knockout plate 78. The upper pressing
surface 78c abuts, from above, an axial end surface of the armature core
7 located in the restraining hole 66a of the radially outer restraining
ring 66. As shown in FIGS. 10(a) and 14, the upper pressing surface 78c
is formed such that it can abut against an axial end surface of the
annular portion 22, which is an annular first pressing region A1
including the fitting recess 16 and the fitting projection 15. The upper
pressing surface 78c is formed such that it can abut against an axial end
surface of each of the teeth 23, which is a second pressing region A2 set
at a radial central portion of each of the teeth 23. The upper pressing
surface 78c is formed such that it can abut against an axial end surface
of each of the teeth 23, which is a third pressing region A3 existing at
the distal end of each of the teeth 23. In FIG. 14, the first pressing
region A1, the second pressing region A2 and the third pressing region A3
are shown by fine dots.

[0074] The upper die 71 is driven by a drive device (not shown).

[0075] In the pressing step using the pressing device 51, the lower die 61
and the upper die 71 are first separated from each other in the vertical
direction. The lower knockout plate 67 is urged by the first spring 65
through the first knockout pressing pin 64, and the first stopper 67a
abuts against the bottom surface of the first stopper recess 66b. The
upper knockout plate 78 is urged by the second spring 75 through the
second knockout pressing pin 74, and the second stopper 78a abuts against
the bottom surface of the second stopper recess 77b. In this state, the
armature core 7 formed in the laminating step is located in the
restraining hole 66a of the radially outer restraining ring 66. The
armature core 7 is inserted into the restraining hole 66a in the axial
direction until the axial end surface of the armature core 7, which is
opposed to the lower knockout plate 67, abuts against the lower pressing
surface 67c. At this time, as shown in FIG. 11, the radially inner
restraining metal core 68 is inserted into the armature core 7. That is,
the radially inner restraining portion 68a is inserted into the distal
end surfaces of the sixty teeth 23 from the axial direction and at the
same time, the sixty distal end restraining portions 68b are inserted
into the sixty slits 24 from the axial direction. The armature core 7
inserted into the restraining hole 66a is restrained by the radially
outer restraining ring 66 from the radial outer side and is restrained by
the radially inner restraining metal core 68 (radially inner restraining
portion 68a) from the radial inner side. The distal ends of the teeth 23
are restrained by the distal end restraining portions 68b from
circumferential both sides. The armature core 7 is restrained from radial
outer and inner sides by the radially outer restraining ring 66 and the
radially inner restraining metal core 68, and the armature core 7 is
arranged coaxially with the edge-removing punches 76 and the upper
knockout plate 78.

[0076] Thereafter, the upper die stage 72 is moved downward by the drive
device (not shown) until the upper pressing surface 78c of the upper
knockout plate 78 abuts against the armature core 7 from the axial
direction. According to this operation, an axial end surface of the
armature core 7 abuts against the upper pressing surface 78c of the upper
knockout plate 78, and the other axial end surface of the armature core 7
abuts against the lower pressing surface 67c of the lower knockout plate
67. That is, as shown in FIG. 10(a), the armature core 7 is fixed from
both axial sides by the upper knockout plate 78 and the lower knockout
plate 67. At this time, by the downward movement of the edge-removing
punch associated with the downward movement of the upper die stage 72,
the introducing portions 76d of the sixty pressing portions 76b are
respectively inserted into the sixty slots S from one axial end openings
of the sixty slots S.

[0077] Thereafter, as shown in FIG. 10(b), the upper die stage 72 is
further moved downward by the drive device. Then, the punch plate 73 and
the edge-removing punches 76 are pressed by the upper die stage 72 and
they are further moved downward, and the inserting portions 76c of the
sixty pressing portions 76b are inserted into the slots S. According to
this operation, the knockout holder 77 is pressed by the punch plate 73
and moved downward. At this time, each of the edge-removing punches 76
independently floats with respect to the punch plate 73 and the upper
knockout plate 78. Hence, the edge-removing, punches 76 permit (absorb)
dimension errors of the position of the slots S in the circumferential
direction and the radial direction within a range of gaps between the
punch plate 73 and the upper knockout plate 78, and the edge-removing
punches 76 are located at positions corresponding to the positions of the
slots S.

[0078] The second spring 75, which is compressed associated with the
downward movement of the upper die stage 72, presses the second knockout
pressing pin 74 downward, and the second knockout pressing pin 74 presses
the upper knockout plate 78. Moreover, the upper knockout plate 78
presses the armature core 7 downward in the axial direction, the lower
knockout plate 67 and the first knockout pressing pin 64 are moved
downward by the pressing force, and therefore the first spring 65 is
compressed. As a result, the armature core 7 is pressed from both sides
in the axial direction and restrained by the lower knockout plate 67 and
the upper knockout plate 78 by urging forces of the first spring 65 and
the second spring 75.

[0079] Restraint of the armature core 7 caused by the lower knockout plate
67 and the upper knockout plate 78 will be described in detail. As shown
in FIGS. 10(b) and 14, the upper pressing surface 78c abuts against the
first pressing region A1. According to this abutment, the annular portion
22 of the armature core 7 is restrained from the axial direction by the
lower knockout plate 67 and the upper knockout plate 78. The upper
pressing surface 78c abuts against the second pressing region A2.
According to this abutment, radial central portions of the teeth 23 of
the armature core 7 are restrained from the axial direction by the lower
knockout plate 67 and the upper knockout plate 78. Further, the upper
pressing surface 78c abuts against the third pressing region A3.
According to this abutment, the distal ends of the teeth 23 of the
armature core 7 are restrained from the axial direction by the lower
knockout plate 67 and the upper knockout plate 78. In the present
embodiment, the magnitude of the restraining force per unit area of the
lower knockout plate 67 and the upper knockout plate 78 to restrain the
annular portion 22 from the axial direction is greater than the magnitude
of the restraining force per unit area of the lower knockout plate 67 and
the upper knockout plate 78 to restrain the distal ends of the teeth 23
from the axial direction. The magnitude of the restraining force, per
unit area, of the lower knockout plate 67 and the upper knockout plate 78
to restrain the distal ends of the teeth 23 from the axial direction is
greater than the magnitude of the restraining force per unit area of the
lower knockout plate 67 and the upper knockout plate 78 to restrain the
radial central portions of the teeth 23 from the axial direction. That
is, among the restraining forces applied to the first to third pressing
regions A1 to A3, the restraining force applied to the first pressing
region A1 is the greatest, and the restraining force applied to the
second pressing region A2 is the smallest.

[0080] As shown in FIGS. 10(b) and 13(b), in a state where the armature
core 7 is restrained from both sides in the axial direction by the lower
knockout plate 67 and the upper knockout plate 78, the edge-removing
punches 76 are further moved downward associated with the downward
movement of the upper die stage 72. Then, the edge-removing surfaces 76e
of the edge-removing punches 76 are pressed against the corner portions K
of the core sheet 11a located at one axial end (upper end in FIG. 10(b))
of the armature core 7. According to this configuration, the arcuate
edge-removed portions 25 are formed on the corner portions K of the core
sheet 11a. At this time, the edge-removing surface 76e comes into contact
only with the core sheet 11a located at one axial end of the armature
core 7 and does not come into contact with another core sheet 11 that is
adjacent to the former core sheet 11a (i.e., second core sheet 11 from
one axial end of armature core 7).

[0081] Thereafter, the upper die stage 72 is moved upward by the drive
device. As the upper die stage 72 is moved upward, the punch plate 73 and
the edge-removing punches 76 are also moved upward. At this time, the
lower knockout plate 67 and the upper knockout plate 78 are pressed
toward the armature core 7 by the urging forces of the first spring 65
and the second spring 75. Hence, the armature core 7 is maintained in a
state where it is restrained from both axial sides by the lower knockout
plate 67 and the upper knockout plate 78. That is, according to the
armature core 7, the annular portion 22, the radial central portions of
the teeth 23 and the distal ends of the teeth 23 are maintained in a
state where they are restrained from the both axial sides by the lower
knockout plate 67 and the upper knockout plate 78. In this state, the
edge-removing punches 76 are moved upward, the corner portions K, on
which the edge-removed portions 25 are formed, are separated from the
edge-removing surfaces 76e. After the state shown in FIG. 10(a) is
established, the upper die 71 is further moved upward, and the armature
core 7 can be taken out from the restraining hole 66a. Thereafter, the
edge-removed portions 25 are formed also on the corner portions K of the
core sheet 11b located on the other axial end side of the armature core
7, located on an end of the armature core 7 opposite from the end on
which the edge-removed portions 25 are first formed.

[0082] Next, as shown in FIG. 15, an insulating member inserting step for
inserting the insulating member 26 into each slot S is carried out. The
insulating member 26 is formed by folding back a square sheet-like
insulating material (not shown) such that both ends of the insulating
material are opposed to each other. The insulating member 26 has a
substantially U-shaped cross section. In the insulating member inserting
step, the insulating member 26 is bent and the insulating member 26 is
inserted into the slot S in the axial direction of the armature core 7
from one axial end opening of the slot S. The insulating member 26 is
inserted into the slot S until the insulating member 26 projects from
both axial side openings of the slot S.

[0083] Next, a spreading step for circumferentially spreading one axial
end of the insulating member 26 projecting in the axial direction from
each slot S is carried out. In the spreading step, a heating forming
device (not shown), which is heated to a predetermined temperature is
brought into contact, under pressure, with one ends of the insulating
members 26, which project from one end openings of the slots S. The
heating forming device can be moved in the axial direction of the
armature core by the drive device (not shown). According to this
operation, the one ends of the insulating members 26 are spread in the
circumferential direction by the heating forming device. That is, as
shown in FIG. 16, spread portions 81, which spread in the circumferential
direction, are formed on one ends of the insulating members 26.

[0084] Next, a conductor inserting step for inserting, from the axial
direction, the segment conductors 27 to interiors of the insulating
members 26 inserted into the slots S is carried out. In the conductor
inserting step, the two straight portions 27a and 27b of each
substantially U-shaped segment conductor 27 are respectively inserted
into two slots S that are separated from each other in the
circumferential direction by the distance corresponding to a
predetermined number of slots S. The straight portions 27a and 27b are
inserted inside the insulating members 26 from the spread portions 81.
The segment conductors 27 are moved relative to the armature core 7 in
the axial direction of the armature core 7 until distal ends of the
straight portions 27a and 27b project outside of the slots S from the
other axial end openings of the slots S, i.e., from openings on a side
opposite from the spread portion 81.

[0085] Next, a bending step for circumferentially bending the distal ends
of the straight portions 27a and 27b, which project from the other axial
end opening of each slot S, is carried out. As shown in FIG. 17, in the
bending step, the straight portions 27a and 27b are pressed against the
edge-removed portions 25 and circumferentially bent in the vicinity of
the edge-removed portions 25 in a state where the insulating member 26 is
located between the straight portions 27a and 27b and the edge-removed
portions 25 provided in the other axial end opening edge of the slot S.
The distal ends of the straight portions 27a and 27b are bent in the
circumferential direction. According to this bending operation, the
distal ends of the straight portions 27a and 27b are located at positions
that are adjacent to other straight portions 27a and 27b, which are to be
connected respectively.

[0086] Next, a connecting step for electrically connecting the straight
portions 27a and 27b is carried out. In the connecting step, the straight
portions 27a and 27b are electrically connected to other straight
portions 27a and 27b by welding. According to this step, the segment
conductors 27 are formed from the segment conductors 27 and the stator 6
is completed.

[0087] Next, operation of the manufacturing method of the stator 6 of the
present embodiment will be described.

[0088] In the pressing device 51 used in the edge-removing step, each of
the edge-removing punches 76 is in the independently floating state with
respect to the punch plate 73 and the upper knockout plate 78. Hence,
each of the edge-removing punches 76 can follow the position of the slot
S. As a result, it is possible to reliably chamfer while suppressing
deformation (distortion) of the teeth 23.

[0089] In the edge-removing step, the corner portions K in the two core
sheets 11a and 11b on both axial ends of the armature core 7 are pressed
and chamfered, and the arcuate edge-removed portions 25 are formed on the
corner portions K. Hence, in the bending step, the contact area between
the insulating member 26 and the corner portions K when the straight
portions 27a and 27b are circumferentially bent while pressing the
straight portions 27a and 27b against the corner portions K becomes
greater than the contact area when the corner portions K do not have the
edge-removed portions 25 and the corner portions K are pointed.
Therefore, when the straight portions 27a and 27b are bent, it is
possible to prevent a great force from being locally applied to the
insulating member 26 which is located between the corner portions K and
the straight portions 27a and 27b. As a result, the insulating member 26
is prevented from being damaged by the axial opening edge of the slot S.

[0090] The present embodiment provides the following advantages.

[0091] (1) In the edge-removing step, corner portions K of the axial
opening edges of the slots S in the two core sheets 11 located on both
axial ends of the armature core 7 are pressed and chamfered. According to
this edge-removing step, the edge-removed portions 25 are formed on the
corner portions K. Hence, when the segment conductors 27 inserted into
the slots S are circumferentially bent in the bending step, even if the
segment conductors 27 are pushed against the axial opening edge of the
slots S, the insulating members 26 located between the segment conductors
27 and the axial opening edge of the slots S are prevented from being
damaged by the axial opening edges of the slots S. Therefore, it is
possible to ensure the insulation properties between the segment
conductors 27 and the armature core 7. Since it is possible to prevent
the insulating member 26 from being damaged only by pressing the corner
portions K of the opening edges of the slots S by the edge-removing
punches 76 in this manner, a new part that is different from the armature
core 7, the segment conductors 27 and the insulating members 26 does not
need to be added. Therefore, it is unnecessary to change the shape of an
existing part such as the armature core 7 to provide the stator 6 with a
new part, and it is unnecessary to provide equipment for manufacturing
the new part. That is, it is possible to prevent the insulating members
26 from being damaged when the segment conductors 27 are bent by adding a
slight manufacturing cost for adding a step for pressing the corner
portions K and removing the edges of the corner portions K of the opening
edges of the slots S in the existing core sheet 11. Even if the corner
portions K of the slots S are pressed and chamfered, the cross-sectional
area of the opening of each slot S is not easily reduced. From this
reason, it is possible to ensure the insulation properties between the
segment conductors 27 and the armature core 7 while preventing the
manufacturing cost from increasing and preventing the space factor from
lowering.

[0092] (2) By inserting the inserting portions 76c into the slots S, it
becomes easy to arrange the edge-removing punches 76 at positions
corresponding to the positions of the slots S, into which the inserting
portions 76c are inserted. Therefore, the edge-removing punches 76 can
easily absorb dimension errors of the slots S. The teeth 23 on both
circumferential sides of each slot S are substantially restrained in the
circumferential direction by the inserting portions 76c inserted into the
slots S. Therefore, it is possible to prevent the teeth 23 from being
deformed in the circumferential direction when the corner portions K of
the slots S in the core sheet 11 located at an axial end of the armature
core 7 are pressed by the edge-removing punches 76.

[0093] (3) The number of edge-removing punches 76 is the same as that of
the slots S, i.e., sixty, and the edge-removing punches 76 independently
correspond to respective slots S. Therefore, dimension errors (positional
deviations of slots S in armature core 7) of all of the slots S can be
permitted by the edge-removing punches 76, which correspond to the
respective slots S. Hence, it is possible to more effectively suppress
the deformation of the teeth 23 located on the both sides of the slots S
in the circumferential direction and to chamfer the corner portions K of
the opening edges of the slots S in the core sheet 11 located at the
axial end of the armature core 7.

[0094] (4) Only the two core sheets 11 located on the both axial ends of
the armature core 7 are chamfered. Therefore, deformation of the teeth 23
caused by the edge-removing operation can be suppressed to a small
degree. As a result, a cogging torque caused by deformation of the distal
ends of the teeth 23 can be prevented from increasing.

[0095] (5) In the pressing step, the corner portions K of the slots S in
the core sheet 11 located at the axial end of the armature core 7 are
pressed by the edge-removing punches 76 in a state where the armature
core 7 is restrained from the radial inner and outer sides of the
armature core 7. Therefore, when the corner portions K of the slots S are
pressed by the edge-removing punches 76, it is possible to prevent the
armature core 7 from deforming in the radial direction.

[0096] (6) In the pressing step, the corner portions K of the opening
edges of the slots S in the core sheet 11 located at the axial end of the
armature core 7 is pressed by the edge-removing punches 76 in a state
where the distal ends of the teeth 23 and the annular portion 22 are
restrained from the axial direction. Therefore, when the corner portions
K are pressed by the edge-removing punches 76, it is possible to prevent
the annular portion 22 and the teeth 23 from deforming in the axial
direction.

[0097] (7) Axially adjacent yoke forming portions 12 are fixed to each
other through the fitting projections 15 and the fitting recesses 16
provided on the yoke forming portions 12. Hence, non-uniform stresses are
generated on portions of the yoke forming portion 12 where the fitting
projections 15 and the fitting recesses 16 are provided, as compared with
other portions of the yoke forming portion 12 where the fitting
projections 15 and the fitting recesses 16 are not provided. Therefore,
in the pressing step, if the corner portions K of the slots S in the core
sheet 11 located at the axial end of the armature core 7 are pressed by
the edge-removing punches 76 without restraining, from the axial
direction, the portions of the annular portion 22 where the fitting
projections 15 and the fitting recesses 16 are provided, deforming forces
that deform the core sheet 11 into various direction are prone to be
generated. Various deforming forces may be also applied to the corner
portions K and the corner portions K may not be excellently chamfered.
Hence, as in the present embodiment, a range of the annular portion 22
including the fitting projections 15 and the fitting recesses 16, i.e.,
the first pressing region A1 in the axial end surface of the armature
core 7 is restrained from the axial direction. According to this
configuration, when the corner portions K are pressed by the
edge-removing punches 76, it is possible to prevent various deforming
forces from being applied to the corner portions K. Therefore, it is
possible to excellently chamfer the corner portions K of the slots S in
the core sheet 11 located at the axial end of the armature core 7. If the
region of the annular portion 22 including the fitting projections 15 and
the fitting recesses 16 is restrained from the axial direction, the
axially adjacent yoke forming portions 12 can be maintained in a state
where they are fixed to each other through the fitting projections 15 and
the fitting recesses 16 even when the edge-removing punches 76 are
pressed against the corner portions K of the core sheet 11 located at the
axial end of the armature core 7.

[0098] (8) In the pressing step, the corner portions K of the opening
edges of the slots S in the core sheet 11 located at the axial end of the
armature core 7 are pressed by the edge-removing punches 76 in a state
where the distal end restraining portions 68b, which restrain the distal
ends of the teeth 23 from the circumferential direction, are inserted
into the slits 24, respectively. Therefore, when the corner portions K is
pressed by the edge-removing punches 76, it is possible to prevent the
distal ends of the teeth 23 from deforming in the circumferential
direction.

[0099] (9) When the pressing step is carried out, the magnitude of a
restraining force per unit area of the lower knockout plate 67 and the
upper knockout plate 78 to restrain the annular portion 22 from the axial
direction is greater than the magnitude of a restraining force per unit
area of the lower knockout plate 67 and the upper knockout plate 78 to
restrain the distal ends of the teeth 23 from the axial direction.
Therefore, by restraining the distal ends of the easily deformable teeth
23 from the axial direction with a smaller restraining force than that of
the annular portion 22, it is possible to chamfer, in a well-balanced
manner, the entire corner portions K of the slots S in the core sheet 11
located at the axial end of the armature core 7.

[0100] (10) In the pressing step, the corner portions K are pressed by the
edge-removing punches 76 and the armature core 7 are separated from the
edge-removing punches 76 in a state where the radial central portions of
the teeth 23 are restrained from the axial direction. Therefore, it is
possible to chamfer the corner portions K of the slots S in the core
sheet 11 located at the axial end of the armature core 7 in a state where
the positions of the teeth 23 are stable. Hence, the corner portions K
can be chamfered more excellently. Further, since the armature core 7 is
separated from the edge-removing punches 76 in the sate where the radial
central portions of the teeth 23 are restrained from the axial direction,
the armature core 7 and the edge-removing punches 76 are easily separated
from each other. Therefore, it is possible to prevent the armature core 7
from biting into the edge-removing punches 76.

[0101] (11) Since the coils (i.e., segment coils 28) are formed from the
segment conductors 27, the space factor can be increased.

[0102] (12) The core sheets 11 that are located at the axial ends of the
armature core 7 and whose corner portions K are chamfered, i.e., the core
sheets 11a and 11b, are made of magnetic material that is softer than
silicon steel sheet. Therefore, it is easy to chamfer the core sheets 11a
and 11b. Of the core sheets 11 constituting the armature core 7, core
sheets 11 other than the core sheets 11a and 11b are formed from silicon
steel sheet through which a magnetic field easily passes. Hence, in the
motor 1 having the stator 6, it is possible to ensure magnetic
performance (magnetic permeability) of about the same level as that of
the conventional technique.

[0103] (13) Each of the yoke forming portions 12 has fitting projections
15 and fitting recesses 16, which fix the axially adjacent yoke forming
portions 12 to positions on the extension lines L2 of the center lines L1
of the tooth forming portions 13. The fitting projections 15 and the
fitting recesses 16 are formed at positions separated, by equal
distances, from the slots S on both sides in the circumferential
direction of the corresponding teeth 23. Therefore, when the corner
portions K are chamfered with respect to the core sheet 11 of the axial
end of the armature core 7, it becomes easy to equalize the deformation
amounts of the core sheets 11 generated on the circumferentially both
sides of the tooth forming portions 13 corresponding to the fitting
projections 15 and the fitting recesses 16. Hence, it is possible to
prevent the core sheet 11 of the axial end of the armature core 7 from
deforming into a distorted shape. Further, it is possible to prevent the
fitting projection 15 and the fitting recess 16 from becoming a magnetic
resistance against a magnetic flux flowing through the annular portion
22.

[0104] (14) The corner portions K of the slots S in the core sheet 11
located at the axial end of the armature core 7 are chamfered. Therefore,
also when the coils (i.e., segment coils 28) are formed from the segment
conductors 27 as in the present embodiment, it is possible to prevent the
insulating members 26 located between the armature core 7 and the
straight portions 27a and 27b from being damaged when the distal ends of
the straight portions 27a and 27b (ends of the straight portions 27a and
27b opposite from the connecting portions 27c) are bent in the
circumferential direction.

[0105] (15) Since the motor 1 includes the consequent-pole type rotor 31,
the number of the magnets 45 mounted on the rotor 31 can be reduced in
half. Therefore, the manufacturing cost of the motor 1 can be reduced.
Since the rotor 31 includes the gaps 46, it is possible to reduce the
rotor 31 in weight and to reduce the entire motor 1 in weight.

[0106] (16) Since the edge-removed portions 25 are formed on the corner
portions K of the opening edges of the slots S, it is possible to prevent
the insulating members 26 from being damaged by the corner portions K
when the insulating members 26 are inserted into the slots S in the
insulating member inserting step. Therefore, it is possible to ensure the
insulation properties between the armature core 7 and the segment
conductors 27 while the insulating members 26 are thinned. As a result,
it is possible to further prevent the manufacturing cost from increasing,
to further prevent the space factor from lowering and to ensure the
insulation properties between the segment conductors 27 and the armature
core 7.

[0107] (17) The slight gaps 79 are formed between the inner peripheral
surface of each punch insertion hole 78b and the outer peripheral surface
of the corresponding pressing portion 76b. Therefore, the edge-removing
punches 76 can easily move relative to the upper knockout plate 78. As a
result, the inserting portions 76c of the edge-removing punches 76 can be
easily inserted into the slots S.

[0108] (18) The truncated square pyramid-shaped introducing portions 76d,
which become thinner toward the distal ends of the inserting portions
76c, are formed on the distal ends of the inserting portions 76c.
Therefore, it is possible to prevent the distal ends of the inserting
portions 76c from coming into contact with the corner portions K by
inserting the inserting portions 76c into the slots S from the
introducing portions 76d.

[0109] The embodiment of the invention may be modified as follows.

[0110] Although the rotor 31 includes the gaps 46 in the above described
embodiment, the rotor 31 does not necessarily need to include the gaps
46. The rotor 31 is not limited to the consequent-pole type rotor. For
example, magnets of a north pole and magnets of a south pole may be
arranged alternately in the circumferential direction. The rotor 31 may
be of a magnet-embedded type rotor in which a magnet is embedded in the
rotor core for every magnetic pole. The number of the magnets 45 of the
rotor 31 is not limited to five and the number may appropriately be
changed.

[0111] In the above described embodiment, the two core sheets 11a and 11b,
which are located at both axial ends of the armature core 7 and on which
the edge-removed portions 25 are formed, are made of magnetic material
that is softer than silicon steel sheet. The core sheets 11 other than
the core sheets 11a and 11b are made of silicon steel sheet.
Alternatively, each of the core sheets 11 located at both axial ends may
be made of magnetic material that is softer than silicon steel sheet, and
remaining core sheets 11 may be made of silicon steel sheet. According to
this configuration also, the same advantage as that of (12) of the above
described embodiment can be obtained. All of the core sheets 11
constituting the armature core 7 may be made of magnetic material that is
softer than silicon steel sheet or may be made of silicon steel sheet.
The core sheet 11 may be made of magnetic material that is softer than
silicon steel sheet, or may be made of steel sheet other than silicon
steel sheet.

[0112] In the above described embodiment, the conductors that are inserted
into the slots S are the substantially U-shaped segment conductors 27,
which constitute the segment coils 28. However, the conductors that are
inserted into the slots S are not limited to the segment conductors 27
and the conductors may be made of copper wires.

[0113] In the above described embodiment, the twelve fitting projections
15 are formed on the extension lines L2 of the center lines L1 of the
twelve tooth forming portions 13 arranged at 30° intervals in the
circumferential direction on the yoke forming portion 12 of each of the
core sheets 11. Further, the twelve fitting recesses 16 are formed on the
surface of the yoke forming portion 12 opposite from the fitting
projections 15. However, the number of the fitting projections 15 and the
number of the fitting recesses 16 are not limited to them. For example,
the fitting projections 15 and the fitting recesses 16, which
respectively correspond to the fitting projections 15, may be formed on
the yoke forming portion 12 at six positions at 60° intervals in
the circumferential direction or at four positions at 90°
intervals in the circumferential direction while taking the magnetic
characteristics of the motor 1 into account. In this case also, the
fitting projections 15 are formed on the extension lines L2 of the center
lines L1 of the tooth forming portions 13, and the fitting recesses 16
are formed on the surface of the yoke forming portion 12 opposite from
the fitting projections 15. The fitting projections 15 and the fitting
recesses 16 may be formed on the yoke forming portion 12 at positions
deviated from the extension lines L2 in the circumferential direction.

[0114] In the pressing step for the above described embodiment, the corner
portions K are pressed by the edge-removing punches 76 and the armature
core 7 is separated from the edge-removing punches 76 in the state where
the radial central portions of the teeth 23 are restrained from the axial
direction. However, it is not absolutely necessary to press the corner
portions K by the edge-removing punches 76 and to separate the armature
core 7 from the edge-removing punches 76 in the state where the radial
central portions of the teeth 23 are restrained from the axial direction.

[0115] In the pressing step of the above described embodiment, the
edge-removing punches 76 press the corner portions K of portion that
become opening edges of the axial opening of the slots S in the core
sheet 11 located at the axial end of the armature core 7 in the state
where the annular portion 22 and the distal ends of the teeth 23 are
restrained from the axial direction. At this time, the magnitude of the
restraining force per unit area of the lower knockout plate 67 and the
upper knockout plate 78 to restrain the annular portion 22 from the axial
direction is greater than the magnitude of the restraining force per unit
area of the lower knockout plate 67 and the upper knockout plate 78 to
restrain the distal ends of the teeth 23 from the axial direction.
However, the magnitude of the restraining force generated in the annular
portion 22 and the magnitude of the restraining force generated in the
distal ends of the teeth 23 are not limited to them. For example, the
magnitude of the restraining force generated in the annular portion 22
per unit area may be set to the same value as the magnitude of the
restraining force generated in the distal ends of the teeth 23 per unit
area. Further, in the pressing step, it is not absolutely necessary to
restrain the annular portion 22 and the distal ends of the teeth 23 from
the axial direction.

[0116] In the pressing step of the above described embodiment, the
edge-removing punches 76 press the corner portions K of the opening edges
of the slots S in the core sheet 11 located at the axial end of the
armature core 7 in the state where the distal end restraining portions
68b, which restrain the distal ends of the teeth 23 from the
circumferential direction, are inserted into the slits 24. However, it is
not absolutely necessary to insert the distal end restraining portions
68b into the slits 24. In this case, the radially inner restraining metal
core 68 includes the radially inner restraining portion 68a only.

[0117] In the pressing step of the above described embodiment, a region of
the annular portion 22 including the fitting projections 15 and the
fitting recesses 16 is restrained from the axial direction. However, a
region of the annular portion 22 that does not include the fitting
projections 15 and the fitting recesses 16 may be restrained from the
axial direction.

[0118] In the pressing step of the above described embodiment, the
edge-removing punches 76 press the corner portions K of the opening edges
of the slots S in the core sheet 11 located at the axial end of the
armature core 7 in the state where the armature core 7 is restrained from
the radial inner and outer sides of the armature core 7. Alternatively,
the armature core 7 may be restrained only from the radial inner side by
the radially inner restraining metal core 68. The armature core 7 may be
restrained only from the radial outer side by the radially outer
restraining ring 66. It is not absolutely necessary to restrain the
armature core 7 from the radial inner and outer sides of the armature
core 7.

[0119] In the above described embodiment, the edge-removed portions 25 are
formed on the two core sheets 11 of both axial ends of the armature core
7. Alternatively, the edge-removed portions 25 may be formed on only any
one of the core sheets 11 of one axial side of the armature core 7, i.e.,
one of the core sheets 11a and 11b.

[0120] In the above described embodiment, the edge-removed portions 25 are
arcuate. However, the shape of the edge-removed portions 25 is not
limited to the arcuate shape (rounded shape), and it may be of a
chamfered shape. In this case, the tapered shape is inclined at
45° to 80° with respect to the axial direction of the
armature core 7 for example. According to this configuration also, the
same advantage as that of the above described embodiment can be obtained.

[0121] The edge-removing step may be carried out any time after the
laminating step and before the insulating member inserting step.

[0122] It is not absolutely necessary to carry out the spreading step.

[0123] In the above described embodiment, the number of the edge-removing
punches 76 is sixty which is the same as the number of the slots S, and
the edge-removing punches 76 respectively correspond to the slots S.
Alternatively, the edge-removing punches 76 may be independent
corresponding to the slots S. For example, the edge-removed portions 25
may be formed on the core sheet 11 located at the axial end of the
armature core 7 using independent twenty edge-removing punches 76 each
corresponding to three slots S arranged in the circumferential direction.
According to this configuration also, the same advantage as that of (1)
of the above described embodiment can be obtained.

[0124] In the above described embodiment, the armature core 7 includes the
sixty teeth 23 and according to this configuration, the armature core 7
includes sixty slots S in the circumferential direction. However, the
number of the teeth 23 (number of slots S) may appropriately be changed.